How can I know if my ultrasonic cleaner is not malfunctioning

There are many methods to check if an ultrasonic cleaner is malfunctioning or working correctly. Two popular methods are doing the foil test and the microscope slide test. Testing should be done repeatedly and in the same condition to be sure that any change in the results is due to the change in the performance of the cleaner and not because of changes in the variables such as different temperature or different solution concentration. If you are a technical person, you can check if the ultrasonic transducer and the ultrasonic generator are working properly. Measure the resistance and capacitance of the transducer and check if the generator is receiving and outputting the correct power level.